How To Braze Aluminum?

As an Amazon Associate, I Earn From Qualifying Purchases.

One perk of knowing how to braze aluminum is that you can do your repairs affordably. The process is inexpensive and helps you repair holes, cracks, or leaks in aluminum. The aluminum brazing equipment is portable, inexpensive, and doesn’t consume much voltage.

The knowledge enables you to repair broken ears, rivets, threads and fabricate aluminum, cast iron and cast aluminum easily, stronger and quickly. The process is easy and you can braze different aluminum alloys.

Most aluminum brazing alloys in all aluminum structures because of their good strength, appearance and excellent corrosion resistance. The melting point of brazing filler used is closer to the aluminum material being joined, but the base metal should not be melted, which means you have to control the temperature. 

The melting point of brazing filler metal and base metal determines the brazing temperature for aluminum assemblies.

Braze Aluminum Welding Basics

Brazing aluminum requires a heat of 800 degrees F and an iron filler in this case aluminum to join the different metals. You can also use the aluminum as a replacement for one metal part that has fallen off or cracked. 

The brazing instructions are simple and easy to follow. The brazing process doesn’t require chemicals, no flux, special cleaners and you are guaranteed 100 percent success. Also, the aluminum brazing equipment is portable and comes with a small torch. 

The brazing processes low voltage current and can handle different aluminum alloys. The repairs are quicker than conventional methods. You can fill any hole regardless of size for threads stronger than original threads. The technique fills holes, cracks, seal leaks, rebuilds ears and permanently bonds flat pieces. 

Materials needed;

aluminum rod, Carbon steel pipe, welding helmet
  • Brazing metal rod like aluminum
  • Carbon steel pipe
  • Auto-darkening welding helmet

Preparation Of Brazing Aluminum

Neutral Flame for Brazing
  • Prepare the environment by ensuring you have proper ventilation and get a welding helmet
  • Get your carbon steel pipe
  • Place the carbon steel pipe between your two fire brick about 3/4” apart
  • Set your oxyacetylene torch and set the flame to neutral
  • Start brazing from the right if you are right-handed or l start from the left if you are left-handed.
  • Melt off the aluminum filler rod piece onto one end of your pipe with the torch. Place a significant amount of molten filler rod on your steel pipe, then use the molten metal to melt more filler rod without using the torch flame.
  • If you see smoke rising from your molten metal, it means you are getting a poor weld.
  • Allow the part to cool naturally after you are done, then remove the flux residue using a wire brush.
  • Observe all safety measures in the workshop to prevent fire hazards or accidents. 
flame of oxyacetylene torch

Advantages Of Using Brazing Over Welding

As much as brazing is like soldering, it uses a lower temperature to melt the filler material to protect the mechanical and physical properties of base metal, ensuring they remain unchanged. It’s the primary reason experts consider brazing a superior process than welding.

Welding changes the metal’s mechanical properties leading to faults in the final weld. Below are advantages of brazing over welding. 

Less Thermal Distortion

The base metal is uniformly heated, leaving it with little thermal distortion. This is possible because brazing doesn’t melt the metal components it’s joining, hence no distortion to the shape. Welding uses more heat, increasing the risk of thermal distortion. Also, it must melt the components being joined, which increases distortion.  

Brazing Leaves The Joints Cleaner

This is because brazing allows tighter control, leaving the joint clean even without using secondary finishing. Welding leaves irregular beads protruding from the welded parts.

Brazing Allows Joining Of Different Metals 

different metal

The process joints two different materials/ metals without affecting their mechanical properties. 

Brazing Can Bond Non-Metal And A Metal Base

Non-metals like metallized ceramics are easy to braze with other metals. 

Brazing Allows Joining Of Thinner Metal Pieces

Brazing allows you to bond two thin base metal pieces without them melting. 

Brazing Is Easy To Automate For Mass Production

Brazing is easy to integrate into mass production as it gives joints that are less sensitive to deviation, allowing you to handle several projects at a far less cost. Welding takes time and is expensive.

Brazing Is Faster And Inexpensive

Automating brazing is easy and you don’t need specialized robotics. This translates into lower costs with the savings passed to customers.

Cleaning And Fluxing Are Sometimes Necessary, Why And How?

Cleaning the brazed parts removes residual flux that can cause corrosion and damage your material. 

Apply flux before brazing to ensure the aluminum material is pure or has no impurities before you join them. Use a brush to flux. Alternatively, coat the aluminum filler with flux prior to blazing.

Before brazing, do pre-cleaning if you want to get leak-tight and strong brazed joints. Solvents or vapor cleaning are adequate for cleaning non-heat-treatable alloys. 

However, for heat-treatable alloys use chemical cleaning or a manual cleaning using a sandpaper or wire brush to remove thicker oxide layers.

Post Brazing Cleaning

After brazing, clean the brazed assemblies because the brazing fluxes speeds up corrosion if they remain on the joined parts. The process removes flux residues and oxide layers formed during blazing through the prickling process.

You can immerse that hot brazed part in boiling water the moment the brazing alloy solidifies because most fluxes are soluble in water. The resulting steam removes the residual flux.

Dip the brazed part in a concentrate nitric acid for 10 minutes to remove any oxide film, then rinse with water to remove the acid. You can use boiling water to speed up drying.

Alternatively,

Dip the brazed parts in a mixture of 10% nitric acid and 0.25% hydrochloric acid solution for 10 minutes at room temperature, then rinse with hot water to clean off residual flux and oxide film completely. 

Aluminum Brazing Filler Metals

There are commercial aluminum brazing filler metals for aluminum alloys that are aluminum base. You can find them as shim stock or wires. 

The convenient way to replace filler metals is to use a brazing sheet, which basically is an aluminum alloy base metal that is coated on both sides or one side. Core or heat-treatable alloys are composed of mainly magnesium or manganese and can be used as filler metals.

Also, you can use a paste of filler metal powder and flux. Common brazing metals have silicon as a melting point depressant with addition of magnesium, copper or zinc.

Final Words 

Brazing aluminum produces stronger bonds and is inexpensive. Besides, you can handle mass production without fearing thermal distortion. Brazing is cheaper than welding because it uses less voltage and is easy to automate.you need the right materials like filler metals, brazing rods to braze aluminum. Let us know if you need clarification. 

 

FAQs

Do You Need Flux To Braze Aluminum?

Yes. It’s a requirement in aluminum brazing operations. The fluxes have varying combination of chlorides and fluorides and come as a dry powder. When doing torch or furnace brazing, you combine the flux with water to get a paste. The active flux temperature is the same as the aluminum alloy active temperature, making it easy to know when you have an ideal torch temperature. 

What Type Of Brazing Rod Is Used For Aluminum?

You need an easy flow rod that is convenient for brazing aluminum base metals. You can use aluminum alloy 5 brazing rod. 

Can You Braze Aluminum With A Propane Torch?

It’s possible, but you must control the environment to prevent heat loss to the surrounding. This ensures there is uniform heating of the brazing joint. Propane torch can permanently join two metals and the equipment is easily available at your local hardware store. 

Is Brazing Aluminum As Strong As Welding?

A brazed joint is strong and when properly done it’s stronger than a welded joint. Brazing hugely relies on surface area adhesion for strength.

What Flux Is Used For Aluminum?

Superior flux is the most ideal for aluminum metal joining. It refines aluminum and improves the melt quality and recovery rate of metallic aluminum.

Can I Use Solder On Aluminum?

Yes, although you need a specialized solder for aluminum that can bond the metal to different base metals effectively. The metal needs heating to at least 300 degrees Celsius to accept solder. Measure the temperature of aluminum and not that of the heat source. Remember, aluminum is a great heat sink, which means you need a higher heat source to get to the right temperature.

Can I Use Silver Solder On Aluminum?

No. Simply because silver solder is strong enough to work on stainless steel or any other alloy doesn’t mean it can handle aluminum. Instead, you can use filler alloy combinations like tin-silver, tin-zinc to create a special aluminum bond.

Can I Use Aluminum Brazing Rods On Steel?

Yes. Aluminum brazing rods can handle steel and perform a variety of tasks like repairing doors, windows, siding and gutters among others. The brazing rods are of high quality content and produce superior strength.

Leave a Comment